The present invention relates to a high efficiency glass-lined combination space and hot water heater provided with a closed circulating circuit through which a predetermined volume of water is circulated and maintained within the tank. The combination heater of the present invention substantially prevents the build-up of deposits and corrosion. Accordingly, a high constant efficiency heater is achieved and the life expectancy of the heater is substantially prolonged. The hot water heater of the present invention provides both space heating and potable domestic hot water.
Indirect water heaters are well known in the art wherein a coil is placed within a hot water tank to which city water is fed at one end of the coil and exits at the other end to feed a domestic hot water supply. The hot water within the tank is also fed city water which is heated and used for domestic application such as washing or bathing, whereas the water within the coil is used for consumption or other specific applications such as for heating baseboards connected to a water convection circuit. With glass-lined water heaters which are continuously fed city water, the reservoir and heating coil is continuously bombarded with deposits including calcium, silicas, silts and ferrous materials. This causes several problems such as the formation of bacteria within the coil of the radiators when the water is stagnant therein. In radiators, the water could be stagnant for long periods of time as these are not utilized during the summer months. Accordingly, bacteria will build up during the hot summer months and when the system is placed back in use, these bacterias are flushed back into the tank. If the water within the tank is utilized for bathing or other use where the human body is in contact with such water, then this contaminated water could inflict serious disease to the user. Legionella is known to occur if stagnant water is mixed with potable water. This can occur in summer months when water is stagnant in old casted water heaters which are disposed in hot rooms and exposed to direct sunlight. If such stagnant water is mixed with potable water it could prove deadly to human beings. This risk is amplified if the city water does not contain the proper quantity of chlorine. A further disadvantage is that the build-up of calcium on the glass-lined surface as well as the heat transfer surface and coils greatly affects the efficiency of the heater.
U.S. Pat. No. 5,165,472 describes a heat exchanger having fluid injectors therein to maintain the hot water in continuous agitation and this has been found suitable to prevent the formation of deposits on the glass lining of the tank as well as on the heat transfer coils. However, because the system is fed fresh water, deposits and water contamination problems will occur in the heating radiators. The patent is more concerned with the elimination of dead zones or dead spots which cause sediment deposits. A further disadvantage is that these systems corrode the copper pipes due to the use of acid water which contains CO2 and these copper pipes can deteriorate within short periods of time such as five years. Accordingly, such heaters cannot be adapted to old radiator systems which are more fragile and which require hot water in the range of 190xc2x0 F.-200xc2x0 F.
Combination water heating and space heating apparatus utilizing the hot water from the same tank is described in U.S. Pat. No. 5,544,645. As described the water heating unit and the space heating unit are coordinately controlled such that priority is given to the potable hot water supply over space heating in the event that sufficient hot water is not available to satisfy both demands. Accordingly, all of the above-mentioned disadvantages of the prior art are exemplified by this type of apparatus. A still further example of a combination water heating and space heating apparatus is described in U.S. Pat. No. 4,222,350.
It is a feature of the present invention to provide a high efficiency, glass-lined, combination space and hot water heater which substantially overcomes the above-mentioned disadvantages of the prior art and wherein life-expectancy is greatly improved.
Another feature of the present invention is to provide a high efficiency, glass-lined, combination space and hot water heater having a closed water circulating circuit connected to radiators for producing heat and wherein the water consists of a predetermined volume which is continuously circulated during use and wherein the water is substantially free of sedimentary, corrosive and other harmful products.
Another feature of the present invention is to provide a high efficiency, glass-lined, combination space and hot water heater having one or more heat exchange coils therein in contact with the hot water for producing domestic hot water independently of the water circulated in the closed circuit.
Another feature of the present invention is to provide a high efficiency, glass-lined combination space and hot water heater providing substantially unobstructed heat transfer and having a longer life expectancy than prior art water heaters for such use.
According to the above features, from a broad aspect, the present invention provides a high efficiency, glass-lined, combination space and hot water heater which comprises an inner tank. An outer casing is spaced about the inner tank and insulation is provided between the outer casing and the inner tank. The inner tank has a glass-lined inner surface. Heater means is provided for heating a predetermined volume of water within the inner tank. An anode extends within the inner tank. A closed water circulating circuit is connected to the inner tank for circulating hot water from the inner tank. Heat exchange means is connected in the closed water circulating circuit. A pump is connected to the closed water circulating circuit for convecting hot water from the inner tank through the heat exchange means. The predetermined volume of recirculating water provides for minimal deposits to accumulate in the inner tank thereby substantially preventing the build-up of deposits on heat exchange elements within the tank and the formation of harmful bacteria and corrosion and further wherein high constant efficiency is achieved and the life expectancy of the hot water heater is substantially prolonged. At least one heat exchange coil is disposed in the inner tank and immersed in the water contained therein. The heat exchange coil is connected at one end to an outlet coupling to which a domestic hot water line is connected. An opposed end of the heat exchange coil is connected to an inlet coupling. The inlet coupling is connected to a pressurized water supply.